Circuit Documentation

Summary

This circuit integrates an Arduino UNO with an RFID-RC522 module, an HC-SR04 Ultrasonic Distance Sensor, and a Servomotor SG90 to create a system that detects objects within a certain distance and checks for RFID tags. If an object is detected within the predefined distance and an RFID tag is present, the servo motor is activated to move to a specified angle.

Component List

Arduino UNO

• Microcontroller board based on the ATmega328P
• It has 14 digital input/output pins, 6 analog inputs, a 16 MHz quartz crystal, a USB connection, a power jack, an ICSP header, and a reset button.

RFID-RC522

• An RFID reader/writer module
• Operates at 13.56 MHz frequency
• Interfaces with microcontrollers via SPI

HC-SR04 Ultrasonic Distance Sensor (Wokwi Compatible)

• An ultrasonic ranging module
• Provides 2cm to 400cm non-contact measurement functionality
• Operates on a 5V power supply

Servomotor SG90

• A small and lightweight servo motor
• Capable of rotating approximately 180 degrees
• Operates on a 5V power supply

Wiring Details

Arduino UNO

• D10 connected to RFID-RC522 SDA
• D13 connected to RFID-RC522 SCK
• D11 connected to RFID-RC522 MOSI
• D12 connected to RFID-RC522 MISO
• Multiple GND pins connected to GND of RFID-RC522, HC-SR04, and Servomotor SG90
• D4 connected to RFID-RC522 RST
• 3.3V connected to RFID-RC522 VCC (3.3V)
• 5V connected to HC-SR04 VCC and Servomotor SG90 VCC
• D3 connected to HC-SR04 TRIG
• D2 connected to HC-SR04 ECHO
• D5 connected to Servomotor SG90 SIG

RFID-RC522

• SDA connected to Arduino UNO D10
• SCK connected to Arduino UNO D13
• MOSI connected to Arduino UNO D11
• MISO connected to Arduino UNO D12
• GND connected to common ground
• RST connected to Arduino UNO D4
• VCC (3.3V) connected to Arduino UNO 3.3V

HC-SR04 Ultrasonic Distance Sensor (Wokwi Compatible)

• VCC connected to Arduino UNO 5V
• TRIG connected to Arduino UNO D3
• ECHO connected to Arduino UNO D2
• GND connected to common ground

Servomotor SG90

• SIG connected to Arduino UNO D5
• VCC connected to Arduino UNO 5V
• GND connected to common ground

Documented Code

#include <Servo.h>
#include <SPI.h>
#include <MFRC522.h>

// Define pins for HC-SR04
const int trigPin = 3;
const int echoPin = 2;

// Define pins for RFID-RC522
#define SS_PIN 10
#define RST_PIN 4
MFRC522 rfid(SS_PIN, RST_PIN);

// Define servo
Servo myServo;
const int servoPin = 5;

// Define distance threshold (in cm)
const int distanceThreshold = 10;

void setup() {
  // Initialize serial communication
  Serial.begin(9600);

  // Initialize pins for HC-SR04
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  // Initialize RFID
  SPI.begin();
  rfid.PCD_Init();

  // Initialize servo
  myServo.attach(servoPin);
  myServo.write(0); // Initial position
}

void loop() {
  // Measure distance using HC-SR04
  long duration, distance;
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = (duration / 2) / 29.1;

  // Check if distance is below threshold
  if (distance < distanceThreshold) {
    // Check for RFID card
    if (rfid.PICC_IsNewCardPresent() && rfid.PICC_ReadCardSerial()) {
      // Turn servo to 60 degrees
      myServo.write(60);
      delay(1000); // Hold position for 1 second
      myServo.write(0); // Return to initial position
    }
  }

  delay(100); // Small delay to avoid excessive polling
}

This code initializes the HC-SR04 sensor, RFID-RC522 module, and Servomotor SG90 on an Arduino UNO. It continuously measures the distance using the ultrasonic sensor and checks for the presence of an RFID tag when an object is detected within a specified threshold. If both conditions are met, the servo motor is activated.